Fabricating Co<sub>9</sub>S<sub>8</sub>@NiWO<sub>4</sub> Electrode toward Record Area Capacitance of 18.8 F cm<sup>–2</sup> for High Performance Supercapacitor
Zheng Cui, Wei Cheng, Yaning Liu, Junsong Liu, Nan Gao, Hongdong Li
Abstract
Realizing ultrahigh area capacitance based on suitable electrodes is a challenge for supercapacitors. In this work, an electrode is designed consisting of Co 9 S 8 nanotubes and NiWO 4 nanoparticles (named Co 9 S 8 @NiWO 4 ) and fabricated by a hydrothermal process. The Co 9 S 8 @NiWO 4 electrode realizes a record area capacitance of 18.8 F cm –2 at a current density of 5 mA cm –2 among the reports in the literature. The corresponding asymmetric supercapacitor shows high energy density of 0.48 mW h cm –2 at 2.42 mW cm –2 and superior cyclic stability of 79.2% retention over 7000 cycles at 10 mA cm –2 . The great promotion in performance of Co 9 S 8 @NiWO 4 electrode is synergistically attributed to high intrinsic theoretical capacitances of compounds, abundance polyvalent states, improved conductivity, and increases in reaction sites and rate of the electrode. This work provides a new route for designing highly efficient electrode for developing supercapacitors with high performance in practical applications.